The present invention relates to a method for manufacturing a magnetic recording medium used in a memory device, in particular a hard disk drive, that is installed in an information memory device of an information processing apparatus such as a computer or any other memory apparatus for private use.
With the present increase in the amount of information handled by information processing apparatus such as a computer, as well as the miniaturization of such an apparatus in recent years, the recording capacity of an information memory device has been enhanced and the recording capacity of a magnetic recording medium used in the information memory device continuously increases. Enhancement of recording density requires a decrease in the bit length. Bit length is the space occupied by a unit of information recording. Minimization of the flying height of a recording head is one technique for reducing the bit length.
To minimize the flying height of the head, eliminating protrusions on the surface of the magnetic recording medium is indispensable. Accordingly, burnishing is conventionally carried out on the surface of the magnetic recording medium using a polishing tape coated with abrasive grains of alumina. Burnishing is usually done after formation of a protective film or before a glide height test after application of liquid lubricant.
However, since the protective film also is being reduced in thickness in recent years, tape-burnishing on the surface of the recording medium after protective film formation generates scratches, which may raise problems in error quality and anti-corrosion.
These problems are significant when a soft plastic substrate is used. The film thickness of a lubricant layer of a recording medium after application of a liquid lubricant on the protective film and before the glide test is at most about 2 nm since the thickness is optimized for attaining good friction characteristics and avoidance of adhesion at head contact. The value of the thickness obtained produces little effect in suppressing scratch generation due to burnishing. Dust and particles are also generated on the surface of the recording medium due to the tape-burnishing. The dust and particles remain after the burnishing process and are drawn into the air stream that is developed by the head flying at low flying height, especially during a seeking operation of the recording medium. As a result, electromagnetic conversion characteristics are significantly affected. In the worst case, head crash occurs, with serious effects on the reliability of the magnetic recording device.
It is an object of the invention to provide a method for producing a magnetic recording medium having improved surface smoothness with reduced scratches and particles on its surface.
Briefly stated, the present invention provides a method for producing a magnetic recording medium in which a lubricating layer is applied to the surface of a thin protective layer on the magnetic recording medium. The surface of the protective layer is burnished to reduce protuberances. The lubricating layer is removed by solvent washing. Then, a replacement lubricating layer is deposited on the surface of the protective layer. The resulting surface of the magnetic recording medium exhibits reduced scratching and particle contamination.
According to an embodiment of the invention, there is provided a method for manufacturing a magnetic recording medium comprising steps of: depositing a non-magnetic metallic under-layer on a substrate, depositing a magnetic layer on the under-layer, depositing a protective layer on the magnetic layer, depositing a lubricating agent on the protective layer, burnishing a surface of the magnetic recording medium, washing the lubricating agent away using a solvent, and depositing a liquid lubricant layer on the protective layer.
A method for burnishing a surface of a magnetic recording medium comprising: depositing a first lubricating layer on the surface, the first lubricating layer being of a type omitting a functional end group, burnishing the surface, solvent washing the surface to remove the first lubricating layer, depositing a second lubricating layer on the surface, and the second lubricating layer being of a type having a functional end group.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.